Light scanning apparatus, adjustment method of light scanning apparatus, and storage medium

Abstract

A scanning assembly configured to reciprocally scan a predetermined scanning range in a first direction with a laser beam by projecting the laser beam reflected by a reflective member periodically driven by an actuator to rotate reciprocally, a retrospective optics configured to guide a light incident on the reflective member to the light detector, and a reflective area configured to specularly reflect the laser beam are provided. Driving frequency of the actuator is adjusted such that a time interval between a first reference timing determined based on detection timing of a light reflected from the reflective area and a second reference timing determined based on a timing when the scan reaches a predetermined end of the scanning range substantially become equal in a forward scan path and a backward scan path of the reciprocating scan passing through the reflective area.

1 . A light scanning apparatus, comprising:
 a scanning assembly configured to reciprocally scan a predetermined scanning range in a first direction with a laser beam by projecting the laser beam reflected by a reflective member periodically driven by an actuator to rotate reciprocally, the reciprocating scan including a forward scan path and a backward scan path;   a light detector configured to receive and detect light at a predetermined position;   a retrospective optics comprising the reflective member and a collective optics, and configured to guide a first light to the light detector, the first light being incident on the reflective member;   a measuring assembly configured to measure time of flight (ToF) value between projection of the laser beam and reception of light by the light detector;   an object detecting assembly configured to detect a distance to an object related to direction of each projection of the laser beam, based on the ToF value measured by the measuring assembly regarding to the each projection of the laser beam;   a first reflective area configured to specularly reflect the laser beam, at a predetermined portion partly overlapping the scanning range in the first direction; and   a frequency adjusting assembly configured to adjust a driving frequency to be applied to the actuator such that, regarding to a time interval between a first reference scan timing determined based on detection timing of a light reflected from the first reflective area in a scan and a second reference scan timing determined based on a timing when the scan reaches a predetermined end of the scanning range, a first value of the time interval along the forward scan path passing through the first reflective area and a second value of the time interval along the backward scan path passing through the first reflective area substantially become equal.   
     
     
         2 . The light scanning apparatus according to  claim 1 ,
 wherein the first reflective area has a generally specular reflective surface configured to specularly reflect the projected laser beam incident thereon substantially into a direction where the retrospective optics guides the reflected laser beam to the light detector, and   the specular reflective surface of the first reflective area is extended at least along the first direction to form a second reflective area and the second reflective area is smoothly continuous with the first reflective area, the second reflective area being configured to specularly reflect the projected laser beam incident thereon to a direction different to that where the retrospective optics guides the reflected laser beam to the light detector.   
     
     
         3 . The light scanning apparatus according to  claim 1 ,
 wherein the frequency adjusting assembly uses:
 an anterior end of the detection timing of the light reflected from the first reflective area in the forward scan path and a posterior end of the detection timing of the light reflected from the first reflective area in the backward scan path; or 
 a posterior end of the detection timing of the light reflected from the first reflective area in the forward scan path and an anterior end of the detection timing of the light reflected from the first reflective area in the backward scan path, 
 as the first reference timing. 
   
     
     
         4 . The light scanning apparatus according to  claim 1 ,
 wherein the scanning assembly is configured to scan the scanning range with the laser beam in a primary scanning direction that is the first direction, and in the secondary scanning direction different from the primary scanning direction, and   the first reflective area is positioned only in a part of the scanning range in the secondary scanning direction such that at least a pair of reciprocating primary scanning lines pass therethrough.   
     
     
         5 . The light scanning apparatus according to  claim 1 , further comprising 
 a determining assembly configured to determine that the projected laser beam is reflected from the first reflective area when the ToF value measured by the measuring assembly is less than a predetermined threshold.   
     
     
         6 . The light scanning apparatus according to  claim 1 , further comprising
 an amplitude adjusting assembly configured to adjust a driving amplitude to be applied to the actuator such that a first period length during which the light detector detects the light reflected from the first reflective area or a second period length during which the light detector does not detect the light reflected from the first reflective area, within one scanning period of a first scan passing through the first reflective area, becomes a predetermined targeted period length.   
     
     
         7 . The light scanning apparatus according to  claim 6 ,
 wherein the amplitude adjusting assembly is configured to adjust the driving amplitude in a state where the first value and the second value of the time interval are substantially equal.   
     
     
         8 . The light scanning apparatus according to  claim 2 , further comprising
 an amplitude adjusting assembly configured to adjust a driving amplitude applied to the actuator such that a first period length during which the light detector detects the light reflected from the first reflective area or a second period length during which the light detector does not detect the light reflected from the first reflective area, within one scanning period of a first scan passing through the first reflective area, becomes a predetermined targeted period length.   
     
     
         9 . The light scanning apparatus according to  claim 8 ,
 wherein the amplitude adjusting assembly is configured to adjust the driving amplitude in a state where the first value and the second value of the time interval are substantially equal.   
     
     
         10 . An adjustment method of a light scanning apparatus, comprising:
 preparing a light scanning apparatus comprising: a scanning assembly configured to reciprocally scan a predetermined scanning range in a first direction with a laser beam by projecting the laser beam reflected by a reflective member periodically driven by an actuator to rotate reciprocally, the reciprocating scan including a forward scan path and a backward scan path; a light detector configured to receive and detect light at a predetermined position; a retrospective optics comprising the reflective member and a collective optics, and configured to guide a first light to the light detector, the first light being incident on the reflective member; a measuring assembly configured to measure time of flight (ToF) value between projection of the laser beam and reception of light by the light detector; an object detecting assembly configured to detect a distance to an object related to direction of each projection of the laser beam, based on the ToF value measured by the measuring assembly regarding to the each projection of the laser beam; and a first reflective area configured to specularly reflect the laser beam, at a predetermined portion partly overlapping the scanning range in the first direction; and   adjusting a driving frequency to be applied to the actuator such that, regarding to a time interval between a first reference scan timing determined based on detection timing of a light reflected from the first reflective area in a scan and a second reference scan timing determined based on a timing when the scan reaches a predetermined end of the scanning range, a first value of the time interval along the forward scan path passing through the first reflective area and a second value of the time interval along the backward scan path passing through the first reflective area substantially become equal.   
     
     
         11 . A non-transitory machine-readable storage medium storing program instructions executable by a processor configured to control a light scanning apparatus comprising: a scanning assembly configured to reciprocally scan a predetermined scanning range in a first direction with a laser beam by projecting the laser beam reflected by a reflective member periodically driven by an actuator to rotate reciprocally, the reciprocating scan including a forward scan path and a backward scan path; a light detector configured to receive and detect light at a predetermined position; a retrospective optics comprising the reflective member and a collective optics, and configured to guide a first light to the light detector, the first light being incident on the reflective member; a measuring assembly configured to measure time of flight (ToF) value between projection of the laser beam and reception of light by the light detector; an object detecting assembly configured to detect a distance to an object related to direction of each projection of the laser beam, based on the ToF value measured by the measuring assembly regarding to the each projection of the laser beam; and a first reflective area configured to specularly reflect the laser beam, at a predetermined portion partly overlapping the scanning range in the first direction,
 and when executed, causing the processor to execute:   adjusting a driving frequency to be applied to the actuator such that, regarding to a time interval between a first reference scan timing determined based on detection timing of a light reflected from the first reflective area in a scan and a second reference scan timing determined based on a timing when the scan reaches a predetermined end of the scanning range, a first value of the time interval along the forward scan path passing through the first reflective area and a second value of the time interval along the backward scan path passing through the first reflective area substantially become equal.